Snap rings have long been used as retainers for removably fastening parts, particularly cylindrical ones, inside cylindrical bores and the like. These rings are split and of uniform thickness end-to-end; however, their width varies in that they generally have a rather wide medial portion tapering in both directions down toward each end where the much wider apertured lugs are located. Suitable plier-like tools having blunted pins for jaws are insertable into the apertures in the lugs and used to spring the ends of the ring together thus releasing the latter from its mounting groove in the bore. The narrowed portions between the medial section and each lug allow for enough spring in the ring to effect its release from the groove. Obviously, upon removal of the snap ring, withdrawal of the retained part becomes possible.
The problem arises when one or both of the lugs break off and there is nothing left for the conventional tool to grab onto. If only one lug is missing, it is oftentimes possible to use an eccentrically-pinned tool like that shown in Boyd's U.S. Pat. No. 4,175,310 to pry at least one end of the ring free of the groove, whereupon, it can generally be extracted by getting a prying tool of some type behind it and working the latter around to the end having the broken-off lug without permitting the end that still has the lug from reentering the groove.
A much greater problem exists when both lugs are broken off because there is no hole left to receive the pin of the removal tool. Even in those instances where enough of one of the lugs remains to grab onto with a plier-like tool but there is no space underneath it due to the close proximity of the retained part or so-called "endplate", the removal of the ring becomes a very difficult chore and one that has been handled in the past all too often by employing techniques, some of which will be outlined later, that end up damaging, if not effectively destroying the cylinder in which the ring is mounted. Most of these techniques are time-consuming, expensive and, most important, destructive of one part of the assembly.
A still further complication is the presence of a center shaft projecting from the endplate which so crowds the workspace that even getting the tool near the broken snap ring ends becomes difficult to say nothing of having enough room to manipulate the ring once it has been gotten ahold of in some fashion.